Process of recovering zinc.



UNITED STATES PATENT OFFICE.

CHARLES J. REED, OF PHILADELPHIA, PENNSYLVANIA.

PROCESS OF RECOVERINQ ZINC.

No Drawing.

To all whom it may concern Be it known that I, CHARLES J. REED, a citizen of the United btates, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Recovering Zinc, of which the following is a specification.

lhe. process is directed to the recovery of zinc from ores, flue dust, chimney fume. etc. If the material containsisnltids, I prefer as a preliminary ope-ratitm to roast it at a low temperature. to convert the sultids into oxids. sulfates and sultites. This mixture, in a. finely pulverized condition, or the original material if it comprises only oxids,

sulfates, sultitesand arbonatcs, is treatedwith sulfur' acid of proper strength, either directly or after a preliminary washing with water to remove the soluble sulfates. I may use acid of any suitable strength, as for example that. having a specific gravity of 1.25. I first ascertam the percentage of zinc contained in the material, and use a quantity of acid either equal to or somewhat in excess of the amount theoretically required to dissolve the zinc present. silveare present, I use'an excess of acid above the amount reqnired to dissolve these metals also. If iron in' a ferrous condition is also present, enoughacid may be used to dissolve some iron also. I find it advantageous to use heat and. agitation in order to effect a complete or nearly complete solution of the zinc, though .I conceive that it might be. accomplished without heator agitation. \Vhen iron in the ferrous condition is present, I prefer to convert it into the ferric state by adding a small quantity of nitric acid, lead peroxid, sodium permanganate, air, or other oxidizing agent which will not interfere with the subsequent operations. The resulting solution containing sulfates of zinc, whatever copper. silver and cadmium may be present. and some iron, is then removed from the insoluble residue, as by filtration or decantation. If necessary, the solution is then again treated With an oxidizing agent such as specified, in order to insure the conversion of.all iron into the' ferric state. The oxidized solution is then digested with mud, carbonate or other compound of zinc capable of precipitating the Specification of Letters Patent.

If copper and copper, silver and iron, using enough ofthe zmc-contannng substance so that some excess remains undissolved; the resulting solution is neutral and pure enough for most connnercial purposes, and the zinc may be recovered from it, either in the metallic state by electrolysis, or as crystallized zinc sulfate by evaporation. If, however, a purer quality of zinc is required. the solution is agitated with finely-divided metallic zinc, preferably with the aid of heat. This removes all silver, copper, cobalt, nickel, arsenic. antimony.bismuth. and other metals that would interfere with the electrol \;tic deposition of pure zinc; 'lhe electrolysis of this solution separates zinc at the cathode, and either-liberates free sulfuric acid; at the anode; or causes it to enter into some other chemical combination. I prefer to use an anode of finely-divided metallic lead. which binds the electrtnrhemically liberated sulfuril acid as lead sulfate, thereby elect-rochemically maintaining the solution neutral.

The expression zinc -containing 'substance. as used in the claims, includes either metallic zinc, or any compound of zinc capable .of removing objectionable impurities.

I claim? 1. Theprocess of recovering zinc, which consists in treating material containing zinc with an excess of sulfuric acid, treating the resulting solution with an oxidizing agent, purifying the oxidized solution with an excess of a zinc-containing substance, further purifying the solution, and recovering the zinc from the purified solution.

2. The process of recovering zinc, which consists in treating material containing zinc with sulfuric acid, treating the resulting so- I p Patented Aug. 5,1913. 7

Application filed June 3, 1912. Serial No. 701,299.

lution with an oxidizing agent, purifylng I i In testimony whereof I affix my signature 1 in presence of two witnesses.

CHARLES J. REED. V 

